Chondromalacia, also called chondromalacia patellae, refers to softening and breakdown of the articular cartilage of the kneecap. This disorder happens most often in young adults and can be caused by:

• Injury.
• Overuse.
• Misalignment of the patella.
• Muscle weakness.

Instead of gliding smoothly across the lower end of the thigh bone, the kneecap rubs against it, roughening the cartilage underneath the kneecap. The damage may range from a slightly abnormal surface of the cartilage to a surface that has been worn away to the bone. Chondromalacia injury happens when a blow to the kneecap tears off either a small piece of cartilage or a large fragment containing a piece of bone, known as osteochondral fracture.

The most frequent symptom of chondromalacia is a dull pain around or under the kneecap that worsens when walking down stairs or hills. A person may also feel pain when climbing stairs or when the knee bears weight as it straightens. The disorder is common in runners and is also seen in skiers, cyclists, and soccer players.

Your description of symptoms and an x ray usually help the doctor make a diagnosis. Although arthroscopy can confirm the diagnosis, it’s not performed unless conservative treatment has failed.

Many doctors recommend that people with chondromalacia perform low-impact exercises that strengthen muscles, particularly muscles of the inner part of the quadriceps, without injuring joints. Swimming, riding a stationary bicycle, and using a cross-country ski machine are examples of good exercises for this condition. Electrical stimulation may also be used to strengthen the muscles.

Increasingly, doctors are using osteochondral grafting, in which a plug of bone and healthy cartilage is harvested from one area and transplanted to the injury site. Another relatively new technique is known as autologous chondrocyte implantation (ACI). It involves harvesting healthy cartilage cells, cultivating them in a lab, and implanting them over the lesion.

If these treatments don’t improve the condition, the doctor may perform arthroscopic surgery to smooth the surface of the cartilage and “wash out” the cartilage fragments that cause the joint to catch during bending and straightening. In more severe cases, surgery may be necessary to correct the angle of the kneecap and relieve friction between it and the cartilage, or to reposition parts that are out of alignment.